Published German patent document DE 196 25 059 discloses a fuel injector having swirl channels (referred to as fuel channels there), which, in their position relative to the axis of the valve needle, are inclined in the direction of the main flow of the fuel. In published German patent document DE 196 25 059, the incline of the swirl channels is used for the injection of a fuel jet directly into the combustion chamber following in the discharge direction, through the swirl chamber disposed downstream from the valve-seat surface in the main-flow direction, and through the spray-discharge orifice. In this context, “directly” means without the jet striking parts of the fuel injector lying downstream from the spray-discharge orifice of the swirl chamber. The objective in this case is to influence the direction, form and the skeining of the emerging fuel cloud.
A disadvantage of the fuel injector known from published German patent document DE 196 25 059 is, in particular, the lack of homogeneity of the produced fuel cloud, which is often undesired, especially in a combustion chamber having a largely symmetrical design, and in gas-exchange devices, ignition devices and injectors arranged largely symmetrically thereto. Furthermore, the swirl generation in the swirl chamber is restricted.
Additional disadvantages result during the manufacture of the swirl channel. In particular, as a result of the fanning out of the laser, the spray-discharge orifice would be damaged by laser drilling in the flow direction of the swirl channel. A so-called lost casting would need to be inserted into the central bore to protect the spray-discharge orifice. The residue left behind in the bore as a result of the lost casting bombardment would have to be removed in an additional production step. Furthermore, such a lost casting is a part that is subject to wear, and it also makes it more difficult to blow off or suction off tiny droplets from the liquefied material produced in the drilling. When laser drilling in another direction, the laser would fan out too much even before reaching the drilling spot, since the laser nozzle from which the laser beam emerges cannot be guided close enough to the drilling site. Furthermore, the angle of the swirl-channel bore cannot be freely moved in the direction of discharge, since the valve-seat surface would then be exposed to the laser beam.